You've probably found yourself in a situation like mine at some point: renew my Mac Book Pro mid-2009 by late 2013 model, or not. A situation with which it is difficult to decide since the price of a Mac Book Pro means that we do not want another newer model to come out a month after buying it and for the same price.
To solve this problem, which can be carried over to any Apple product (iPhone, iPad, iPod, Mac Pro), the guys at Mac Rumors have put together a buying guide that has been on the web for some time. A guide where to know when the product is renewed and recommendations to buy or wait a few months.
In the guide we will see all Apple products classified by iDevices, laptops, desktops, and others. All appear next to a colored 'led' in which the status of the product will be indicated a priori with a view to its purchase.
If we see that the product's LED is green, it is advisable to buy the deviceIt has been very little time since its last renewal and you will be a good purchase since its next generation will take time to arrive. A yellow LED means that the product is in the middle of its renewal cycleYou will not make a bad purchase but it is likely that a short period of time they will renew the range of products.
If, on the other hand, you meet a red led is not recommended at all to purchase the device since the product is expected to be renewed in a fairly short time.
In the end the purchase will depend on your needs, but it is clear that if you do not need the product and you are only thinking of 'updating' it, it is best to consult this guide. It will also give you data on the renewal cycles of the products and the news that they have been having.
Link - Mac Buyer's Guide
More information - The new MacBook Pros in the hands of iFixit